Page contents

According to the Daily Mail, “banned bath salts ‘may be as addictive as cocaine’.” The newspaper went on to say that mephedrone, one of a group of substances also known as “bath salts”, affects the brain’s reward circuits in a manner comparable to that seen with similar doses of cocaine.

Mephedrone (or meow meow) was one of the big news stories of 2010 when it was introduced to the UK as a legal high. Many legal highs were marketed as bath salts or plant foods ‘not fit for human consumption’ to sidestep the strict regulations concerning the sale of medications. Mephedrone was quickly made illegal by the Home Office after concerns were raised about its potential for both addiction and harm.

The Mail’s story is based on a small study in mice that examined the behavioural effect of mephedrone compared to cocaine and to a placebo (dummy drug).

The researchers were examining whether mephedrone would activate the brain’s reward circuits in mice. These are regions of the brain that can cause both physical and emotional pleasure.

The researchers found that mephedrone had a roughly similar effect on the reward circuits as cocaine.

The findings of the study, while interesting, are not especially surprising. Many illegal stimulants such as cocaine, crack and amphetamines have been found to be potentially very addictive. Mephedrone, which has a similar stimulant effect, is likely to have the same potential.

However, the Mail’s claim that mephedrone is ‘addictive as cocaine’ was never directly examined by the researchers.

Research into mephedrone and both its behavioural and biological effects is likely to continue.

Where did the story come from?

The study was carried out by researchers from the University of North Carolina at Chapel Hill in the US and was funded by The US National Institutes of Health and the UNC Bowles Center for Alcohol Studies.

The study was published in the peer-reviewed journal Behavioural Brain Research.

The Daily Mail story accurately reflected the research and the conclusions presented by the researchers, though the use of the word ‘cannibal’ in the headline appeared simply for attention-grabbing purposes. Indeed, it is not clear why the Mail has chosen to publish a story about this research, beyond its topical relation to the incident - film footage of which has been extremely popular on the internet.

What kind of research was this?

This animal study modelled the effects of mephedrone (or ‘meow-meow’) on the brain circuits responsible for producing the neurotransmitter dopamine. Dopamine is involved in the brain’s reward system, and the dopamine circuits are involved in drug reinforcement and drug-seeking behaviours. Drugs that activate this system are likely to be abused. Cocaine and methamphetamines have been shown to activate this circuit. Mephedrone is in a class of drugs called cathinone-derived synthetic stimulants, more commonly known on the street as ‘bath salts’.

Animal studies can give us an idea of the impact of a given drug, and well-validated animal models can provide valuable information to inform further research. The extent to which the results of animal studies can be generalised to humans is unknown, and caution should be exercised when interpreting the results of these types of studies. They can be useful in areas of research that would not be ethical to study in humans, for instance, in the effect of illegal drugs on the brain.

What did the research involve?

The research used an animal model to compare the impact of mephedrone and cocaine on stimulation-seeking behaviours. The behavioural model used was called intracranial self-stimulation. This involves implanting electrodes into the brains of six mice, and training the mice to turn a wheel in order to activate the electrode and stimulate the brain.

The area of the brain targeted by the electrodes is called the medial forebrain bundle (MFB), which is involved with the production of dopamine; thus, when this area is stimulated, the brain’s reward circuit is activated. Drugs that are abused, such as cocaine, reduce the amount of brain stimulation required for the mice to continuously behave in a way that leads to reward.

The researchers recorded the amount of brain stimulation required to maintain the same level of behaviour, or same number of wheel turns during a 50-second time period. They recorded the stimulation required to do this before the mice were exposed to any drugs, and after being given mephedrone, cocaine or a placebo control.

What were the basic results?

The researchers found that exposure to mephedrone lowered the amount of brain stimulation required to illicit the same levels of reward-seeking behaviour. The more mephedrone the mice were given, the less brain stimulation they required. Similar patterns were seen in mice given cocaine.

How did the researchers interpret the results?

The researchers concluded that their results indicate that mephedrone ‘has a high potential for abuse’.

Conclusion

This study found that mephedrone (bath salts or 'meow meow') alters reward-seeking behaviour in a manner similar to cocaine. It is important to remember that this study was conducted in just six mice, and did not examine mephedrone’s impact on human drug-seeking behaviour.

This research suggests that mephedrone activates the area of the brain responsible for signalling reward and reinforcing behaviour. This brain region has also been implicated in reinforcing drug-seeking behaviour. Whether this research translates into mephedrone abuse or addiction in humans is unknown. Though smaller studies do point towards a potential for addiction.

The use of mephedrone – part of the cathinone-derived group of stimulants - has been increasing in recent years, and has several effects similar to other stimulant drugs. According to the researchers, several mephedrone-related deaths have been reported. Research into the effects of the drug is ongoing. In the UK, mephedrone is a class B drug, which is illegal to possess or sell.

Ultimately, this research may help to inform policy regarding the classification of mephedrone but has little direct impact on health.